The Accuracy of the Vigileo/FloTrac System Has Been Improved ...

The Accuracy of the Vigileo/FloTrac System Has Been Improved—Follow-up
After a Software Update: A Blinded Comparative Study of
30 Cardiosurgical Patients
To the Editor:
The Vigileo pulse contour cardiac output system (Edwards Lifesciences, Irvine, CA), especially in its first version, was
controversial regarding its accuracy. 1-12 The authors presented an evaluation of the system in its first software version (1.01). 1
Since then, Vigileo has undergone further software development: the algorithm has been improved, and the data sampling rate
has been accelerated from 20 minutes to 1 minute. This was reason enough to perform a second validation study of the
improved software (version 1.10) with the same method as before in order to evaluate the current status of its accuracy. Only
the site of the arterial catheter differs from the previous study, since we found that the results obtained by femoral artery
catheters did not differ from those obtained by radial artery catheters. Therefore, we used only radial artery cannulae in this
investigation.
After approval by the ethics committee and with written informed consent, 30 patients undergoing coronary artery bypass graft surgery
with extracorporeal circulation were studied. The statistical evaluation was performed by using the Bland-Altman 13 method of analysis.
In addition, a �20% deviation from the pulmonary artery catheter thermodilution technique was evaluated (20% criteria). 14 Synchronized
measurements using both methods were made at 7 predefined time points, intra- and postoperatively, producing 210 data pairs. The
demographic data of the included patients were found comparable. Thus, the improvements regarding the precision are not influenced by
patient characteristics but by the modified properties of the Vigileo system itself.
The recorded data of 6 of the 30 patients had to be excluded because of technical complications (loss of data or incorrect recording
because of the complicated handling of the data transfer). Thus, only 138 of the 210 data pairs were available for analysis. A descriptive,
cumulative presentation of all data pairs is shown in Figure 1. Thirty-one percent of all measurements at the 7 time points did not meet
the 20% criteria (former study, 46%), which is graphically shown in Figure 1. The Bland-Altman plots showed similar results. The
cumulative presentation of all data in the Bland-Altman diagram is shown in Figure 2. At the low bias between the methods (0.04 L/min),
the limits of agreement were �2.13 L/min (�3.0 L/min in the former study).
In our first evaluation, the system had not met the 20% criteria (ie, 75% of all data pairs should be within a �20% range).
In the new evaluation, this situation has improved; 69% of data pairs were found within the �20% limits. The results are
better, and the values are now very close to the strict limits published by Critchley and Critchley. 14
Reflecting the Critchley criteria (20% limits) and the results according to Bland-Altman (1.96� ��2.13 L/min), the accuracy of the
Vigileo system has improved, although the narrow precision criteria are not yet completely met. Therefore, the authors are of the opinion
that the device should not yet be used during and after cardiac surgery because the deviation from the clinical standard method is still out
of scale. However, we expect that further development of the system will improve its accuracy. Future validation studies after evolution
of the Vigileo system should be considered.
PA (L/min)
12.0
11.0
10.0
9.0
8.0
7.0
6.0
5.0
4.0
3.0
2.0
1.0
ARTICLE IN PRESS
0.0
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0
Vigileo (L/min)
y = 0.5027x + 2.5402
R 2 = 0.323
Andreas Zimmermann, MD*
Joachim Steinwendner, PhD*
Stephan Hofbauer, MD*
Michael Kirnbauer, MD*
Jens Schneider, MD†
Leo Moser, MD*
Fig 1. A cumulative presentation of all data pairs. Unit: L/min. PA, pulmonary artery catheter. The broad line is the line of optimum agreement.
The small lines show �20% criterion of agreement; 31% (n � 43) of all data exceeded the 20% limits. (Color version of figure is available online.)
Journal of Cardiothoracic and Vascular Anesthesia, Vol xx, No x (Month), 2009: pp xxx
1

difference: (Vigileo-PA) (L/min)
4.00
3.00
2.00
1.00
0.00
0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00
-1.00
-2.00
-3.00
-4.00
ARTICLE IN PRESS
2 LETTER TO THE EDITOR
mean: (Vigileo+PA)/2 (L/min)
Gernot Pauser, MD*
Departments of *Anaesthesiology and Intensive Care Medicine and †Cardiac Surgery
Paracelsus Medical University
Salzburg, Austria
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Anesth 22:388-393, 2008
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monitoring devices in patients undergoing cardiac surgery. Br J Anaesth 99:329-336, 2007
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bypass grafting with pulmonary artery cardiac output measurements. Eur J Anaesthesiol 24:832-839, 2007
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11. Sander M, Spies CD, Foer A, et al: Cardiac output measurement by arterial waveform analysis in cardiac surgery—A comparison of
measurements derived from waveforms of the radial artery versus the ascending aorta. J Int Med Res 36:414-419, 2008
12. Sander M, Spies CD, Grubitzsch H, et al: Comparison of uncalibrated arterial waveform analysis in cardiac surgery patients with
thermodilution cardiac output measurements. Crit Care 10:R164, 2006
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14. Critchley LA, Critchley JA: A meta-analysis of studies using bias and precision statistics to compare cardiac output measurement techniques.
J Clin Monit Comput 15:85-91, 1999
2.089
0.04
-2.170
Fig 2. Pooled Bland-Altman plot of Vigileo
and pulmonary artery catheter data; 95% prediction
intervals correspond to the limits of agreement
(1.96� ��2.13 L/min). (Color version of
figure is available online.)
doi:10.1053/j.jvca.2008.12.012